Unless otherwise indicated herein, the description provided in this section is not itself prior art to the claims and is not admitted to be prior art by inclusion in this section.
To provide cellular wireless communication service, a wireless service provider typically operates a radio access network (RAN) that includes a number of base stations that radiate to define wireless coverage areas, such as cells and cell sectors, in which wireless communication devices (WCDs) such as cell phones, tablet computers, tracking devices, embedded wireless modules, and other wirelessly-equipped communication devices, can operate. In turn, each base station may be coupled with network infrastructure that provides connectivity with one or more transport networks, such as the public switched telephone network (PSTN) and/or the Internet for instance. With this arrangement, a WCD within coverage of the RAN may engage in air interface communication with a base station and may thereby communicate via the base station with various remote network entities or with other WCDs served by the base station.
In general, a RAN may operate in accordance with a particular air interface protocol or “radio access technology,” with a communication pathway from the base stations to WCDs defining a downlink or forward link and communications from the WCDs to the base stations defining an uplink or reverse link. Examples of existing air interface protocols include, without limitation, Orthogonal Frequency Division Multiple Access (OFDMA (e.g., Long Term Evolution (LTE) or Wireless Interoperability for Microwave Access (WiMAX)), Code Division Multiple Access (CDMA) (e.g., 1×RTT and 1×EV-DO), and Global System for Mobile Communications (GSM), among others. Each protocol may define its own procedures for registration of WCDs, initiation of communications, handoff between coverage areas, and functions related to air interface communication.
In accordance with the air interface protocol, each coverage area may operate on one or more carrier frequencies or blocks of frequencies (e.g., frequency bands, such as 698-960 MHz, 1610-2025 MHz, etc.) and may define a number of air interface channels for carrying information between the base station and WCDs. These channels may be defined in various ways, such as through frequency division multiplexing, time division multiplexing, and/or code-division multiplexing, for instance. By way of example, each coverage area may define a pilot channel, reference channel, or other resource on which the base station may broadcast a pilot signal, reference signal, or the like that WCDs may detect as an indication of coverage and may measure to evaluate coverage strength. As another example, each coverage area may define one or more uplink control channels or other resources on which WCDs may transmit control messages to the base station. And each coverage area may define one or more downlink control channels or other resources on which the base station may transmit control messages or other information to WCDs.
Further, each coverage area may define one or more traffic channels or other resources for carrying bearer communication traffic such (e.g., user traffic or application level traffic) as voice data and other data between the base station and WCDs. Additionally, each link between the BTS and WCD may operate independently from the other links. And, each link between the BTS and WCD may operate on a frequency that is different from the frequency on which each other link operates.
When a WCD first powers on or enters into a base station's coverage area, the WCD may register with the RAN in that coverage area by transmitting a registration request, such as an attach request, to the base station serving that coverage area. The attach request may cause the base station or associated infrastructure to authenticate and authorize the WCD for service by the base station and to reserve network resources for use to serve the WCD. In particular, the attach request may result in setup of one or more logical bearer connections extending in the network between the base station and one or more transport networks and extending over the air interface as a radio link between the base station and the WCD.
Once the WCD is attached with a base station, the WCD may operate in a connected mode or an idle mode. In the connected mode, the WCD may engage in communication of bearer data (e.g., application layer communications, such as SIP signaling, voice communication, video communication, file transfer, gaming communication, or the like), transmitting bearer data on uplink traffic channel resources to the base station and receiving bearer on downlink traffic channel resources from the base station.